In a mobile communication system that is capable of transmitting and receiving signals at various carrier frequency bands, an antenna is usually shared by various corresponding Intermediate Frequency (IF) and/or baseband circuits through a Radio Frequency (RF) switch circuit. The term “RF” usually refers to a radio wave having a frequency ranging from about 3 kHz to 300 GHz. When the mobile communication system is operated to use the antenna to transmit or receive signals according to a predetermined communication protocol at a predetermined carrier frequency band, the RF switch circuit is set to couple the antenna with the corresponding IF and/or baseband sub-circuits and decouple the antenna from other IF and/or baseband sub-circuits. An RF switch circuit that selectively couples a common port to one of a plurality of RF switch ports is also referred to as a Single-Pole Multi-Throw switch circuit.